本体觉传入纤维在小鼠脊髓内的发育变化

目的观察本体觉传入纤维在小鼠脊髓内投射和终止的发育变化。方法采用小牛白蛋白（PV）免疫组织化学染色特异标记本体觉传入纤维，用免疫荧光单标记和双标记方法观察本体觉传入纤维在脊髓内的生长模式以及与运动神经元的关系。染色后的切片用激光共聚焦显微镜进行观察。结果PV样免疫阳性（LI）本体觉纤维最早于胚胎（E）14d出现在后索，E15时进入脊髓灰质。E16时，已有较多的PV—LI纤维到达中间带灰质和前角（VH）。此后，随着发育阶段的增长，脊髓VH内PV—LI本体觉纤维和终末的数量和密度逐渐增加，并在生后早期P0-P7达到最高水平。P14后，上述本体觉纤维和终末的数量逐渐减少。本体觉传入纤维的终末在E17时开始与脊髓VH运动神经元形成密切的接触。结论本体觉传入纤维在脊髓内的定位模式形成于小鼠胚胎后期和生后早期，本研究结果为深入理解脊髓反射运动环路的发育特点提供了依据。

DEVELOPMENTAL ALTERNATIONS IN PROPRIOCEPTIVE AFFERENT PROJECTIONS IN THE MOUSE SPINAL CORD

Objective To observe the developmental changes of projection and termination of proprioceptive afferent fibers in the mouse spinal cord. Methods Parvalbumin(PV) immunohistochemistry was used to label the proprioceptive afferents.Single and dual immunofluorescence histochemistry were used to examine the growth pattern of proprioceptive afferents and their relationships with motoneurons in the spinal ventral horn(VH).The stained sections were observed under a confocal laser_scanning microscope. Results PV_like immunoreactive(LI) proprioceptive fibers first appeared in the dorsal column on embryonic(E) day 14,then entered the gray matter on E15 and reached the intermediate gray matter and VH more obviously on E16.The number and intensity of PV_LI proprioceptive afferent fibers and punctata increased in the VH with age and reached a maximum during earlier postnatal(P) period(P0_P7).After P14,the number and intensity of proprioceptive afferents gradually decreased.The proprioceptive terminals seemed to form close relationship with motoneurons from E17.Conclusion The present study indicates that the somatotopic organization of proprioceptive afferents in the spinal cord is established during the late embryonic and early postnatal stages.These results provide evidence for understanding the development of the reflex movements.